1. Technology Field
The present invention generally relates to optical modules including optical transmitters. In particular, the present invention relates to a control system for a thermoelectric cooler included in communications modules having optical transmitters such that power consumption of the TEC and module is efficiently controlled.
2. The Related Technology
Computing and networking technology have transformed our world. As the amount of information communicated over networks has increased, high-speed transmission has become ever more critical. Many high-speed data transmission networks rely on optical modules such as optical transceivers and similar devices for facilitating transmission and reception of digital data embodied in the form of optical signals over optical fibers. Optical networks are thus found in a wide variety of high-speed applications ranging from as modest as a small Local Area Network (LAN) to as grandiose as the backbone of the Internet.
Typically, data transmission in such networks is implemented by way of an optical transmitter (also referred to as an electro-optic transducer), such as a laser or Light Emitting Diode (LED). The electro-optic transducer emits light when current is passed there through, the intensity of the emitted light being a function of the current magnitude through the transducer. Data reception is generally implemented by way of an optical receiver (also referred to as an optoelectronic transducer), an example of which is a photodiode. The optoelectronic transducer receives light and generates a current, the magnitude of the generated current being a function of the intensity of the received light.
Various other components are also employed by the optical transceiver to aid in the control of the optical transmit and receive components, as well as the processing of various data and other signals. For example, such optical transceivers typically include an electro-optic transducer driver (e.g., referred to as a “laser driver” when used to drive a laser signal) configured to control the operation of the optical transmitter in response to various control inputs. The optical transceiver also generally includes an amplifier (e.g., often referred to as a “post-amplifier”) configured to perform various operations with respect to certain parameters of a data signal received by the optical receiver. A controller circuit (hereinafter referred to the “controller”) controls the operation of the laser driver and post amplifier.
Performance characteristics of an optical transmitter and receiver may vary in response to changes in operational conditions like temperature and voltage. Particularly, changes in temperature may affect the output wavelength of an LED or laser diode; i.e., as the laser temperature varies, a corresponding shift in wavelength of the optical signal simultaneously occurs. One way of controlling temperature of an LED or laser diode, and thereby stabilizing the wavelength of the optical signal, is by using a thermoelectric cooler (TEC).
Generally, a TEC is a device where current flow through the device will heat one side of the device while cooling the other side of the device. The side that is heated and the side that is cooled are controlled by the direction of the current flow. Thus, current flow in one direction will heat a first side while the same first side will be cooled when the current flow is reversed. Thus, by varying the current direction, a TEC connected to a laser or photodiode may be used to either heat or cool the laser or LED to maintain a constant operating temperature.
It is also desirable that the transceiver minimize power use. This is especially true in optical transceivers because various standards and multi source agreements (MSAs) dictate the amount of total power that may be consumed by an optical transceiver. However, TECs contribute to the overall power consumption of the optical transceiver module. Where applications or vendors require or desire relatively lower module power consumption, a need exists in the art for optical transmitter TEC systems that efficiently manage power usage so as to prevent undesired or excessive power requirements while effectively stabilizing the temperature of the laser.